2022/09/06 by G. D. Sutcliffe, P. J. Adrian, Sutcliffe, G. D. +15
Engineering · Physics and Astronomy · #Laser-induced spectroscopy and plasma #Dust and Plasma Wave Phenomena #Ionosphere and magnetosphere dynamics
paper · pdf · doi:10.48550/arxiv.2209.02565
We present experimental observations of electron-scale structures in an expanding high-energy-density (HED) plasma generated with a modest intensity ∼ 2 × 1014 W/cm2, ∼1 ns laser. The observed structures have wavelengths (∼ 150-220 μm) and growth rates (∼ 0.4-1.0 ns-1) consistent with an electron-driven Weibel instability where the anisotropy in the electron distribution is small, A∼ 0.002. This instability is found to be a better match to the observed phenomena than other typical field-generation mechanisms found in HED plasmas, including counter-streaming ion Weibel and magnetothermal instabilities. These observations experimentally demonstrate for the first time that the electron Weibel instability must be considered alongside other magnetic field generation and amplification mechanisms in expanding ablation plasmas, which are ubiquitous in HED research. They also provide physics insight into the generation of magnetic fields in large-scale astrophysical plasmas. Additionally, inspection of the magnetic power spectrum shows a possible scaling match to analytic gyrokinetic predictions, |Bk|2∝ k-16/3, at scales below the electron Larmor radius.